单选题：若a、b、c1、c2、x、y均是整型变量，以下正确的switch语句是

若a、b、c1、c2、x、y均是整型变量，以下正确的switch语句是 @[D](2)
A.
```c++
switch(a+b);
{ case 1: y=a+b; break;
case 0:y=a-b; break;}
```
B.
```c++
switch(a*a+b*b)
{
case 3:
case 1: y=a+b; break;
case 3: y=b-a, break;}
```
C.
```c++
switch a
{ case c1: y=a-b; break;
case c2: x=a*b; break;
default: x=a+b; }
```
D.
```c++
switch(a-b)
{ default: y=a*b; break;
case 3: case 4: x=a+b; break;
case 10: case 11: y=a-b; break; }
```





A.
```c++
switch(a+b);
{ case 1: y=a+b; break;
case 0:y=a-b; break;}
```
B.
```c++
switch(a*a+b*b)
{
case 3:
case 1: y=a+b; break;
case 3: y=b-a, break;}
```
C.
```c++
switch a
{ case c1: y=a-b; break;
case c2: x=a*b; break;
default: x=a+b; }
```
D.
```c++
switch(a-b)
{ default: y=a*b; break;
case 3: case 4: x=a+b; break;
case 10: case 11: y=a-b; break; }
```


答案：D